Well I would have assumed that was pretty obvious. Although you could always just back your DVDs up on your hard drive if you were so inclined.
Edit :
Why would you use iDVD? Just encode to MPEG-4 and then use Toast to burn the DVD.
As for quality of course it is going to be worse. You go from the original source material when the film was made to DVD which uses MPEG-2 video - a lossy format, which you rip and encode using Handbrake to another lossy format and then back to MPEG-2 when you burn the DVD. That is three lots of quality degradation. The best way as you say is to rip using Mac the Ripper and either store it on your hard drive or NAS or burn it using Toast using the correct sized DVD so dual or single layer depending on the film.
Which is what we have just explained.